High Power RF Testing of High Temperature Superconductors

Superconducting materials such as niobium have become extremely useful for accelerator technology, but require low temperature operation ~2 K. The development of high temperature superconductors (HTS) is promising due to their operating temperatures being closer to that of liquid nitrogen ~77 K. This work aims to determine the high-power RF performance of these materials at X-band (11.424 GHz). We have tested two types of rare earth barium copper oxide (REBCO) coatings on copper substrates, film deposited by electron-beam physical vapor deposition, and coated conductors soldered to a copper substrate. RF testing was done via a hemispherical TE mode cavity that maximizes the magnetic field and minimizes the electric field on a 2-inch sample region. We report on conductivity vs temperature measurements at low and high power up to ~1.6 kW input power. Thus far we have so far only observed quenching at temperatures above 80 K, very close to the material's critical temperature.